Colletotrichum truncatum: an unusual pathogen causing mycotic keratitis and endophthalmitis

Abstract

In recent years, the well-known plant pathogens of the Colletotrichum genus were increasingly reported to cause ophthalmic infections in humans. Among 66 species in the Colletotrichum genus, only a few are known to be pathogenic for humans. We report here five cases of ophthalmic infections due to Colletotrichum truncatum, a species never reported earlier to cause human infection. The isolates were identified by morphological characteristics and the sequencing of internal spacer regions of ribosomal DNA. The progress of lesions in those patients was slow compared to that of lesions caused by Aspergillus or Fusarium infections. The surgical management included total penetrating keratoplasty in patients with keratitis and pars plana vitrectomy in endophthalmitis. Two patients were treated additionally with intravitreal amphotericin B deoxycholate, one patient with oral itraconazole, and another patient with oral and topical fluconazole therapy. The present series therefore highlights the expanding spectrum of agents causing eye infections and the inclusion of C. truncatum as a human pathogen.

Fig. 1.

Colonies of Colletotrichum truncatum (NCCPF 112007) as noted on oatmeal agar after 10 days of incubation. (A) Obverse image; (B) reverse image. (C) Lactophenol cotton blue mount of Colletotrichum truncatum (NCCPF 112007) showing the appresoria (black arrow) and falcate nonseptate conidia (white arrow). (D) Acervuli (white arrow) containing setae (black arrow).

Fig. 2.

Phylogram generated using the maximum composite likelihood method based on rDNA ITS sequence data. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1,000 replicates) is shown next to the branches. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. Fusarium oxysporum was used as an outgroup.